A typical a sod harvester cuts a slab of sod and rolls each slab into a cylindrical roll. The sod rolls are then transferred to and stacked on a pallet for delivery. Various mechanized sod handling equipment is known in the prior art. Of particular interest here, are mechanized devices for picking up rolls of sod. For example, U.S. Pat. Nos. 6,296,063 and 6,364,027 both disclose a sod roll pickup mechanism that incorporates a plurality of retractable spears for piercing engagement with a set of sod rolls. Pairs of spear sets extend at an angle with respect to each other from the pickup mechanism to pierce the rolls, thereby capturing the sod rolls. Once the sod rolls are captured by the spears they may be lifted and placed on a carrier or pallet, for example.
In early sod roll pickup mechanisms, the spears are extended and retracted by a power drive mechanism comprising a series of sprockets and chains driven by a motor, such as a hydraulic motor. While the chain and sprocket arrangement of previous sod roll pickup mechanism's is satisfactory for operating the spears, multiple chains and sprockets require constant maintenance to prevent premature failure. Furthermore, a chain drive spear mechanism must operate within certain speed limits to ensure reliability.
Accordingly, there is a need for an improved sod roll pickup mechanism that can operate at higher speeds with increased reliability and less maintenance.